Prototype
The prototype is an object that is associated with every functions and objects by default in JavaScript.
Whenever we create a function , object or array javacript by default attaches a prototype object to it which contains some additional methods inside it.
All JavaScript objects inherit properties and methods from a prototype:
- Date objects inherit from Date.prototype.
- Array objects inherit from Array.prototype.
- Player objects inherit from Player.prototype.
- The Object.prototype is on top of the prototype inheritance chain. Date objects, Array objects, and Player objects all inherit from Object.prototype. The Prototype Chain Prototypal inheritance uses the concept of prototype chaining.
Every object created contains [[Prototype]], which points either to another object or null.
Example:- An object C with a [[Prototype]] property that points to object B. Object B’s [[Prototype]] property points to prototype object A. This continues onward, forming a kind of chain called the prototype chain.
Prototypal Inheritance
let animal = {
eats: true
walk() {
console.log("Animal walk");
}
};
let rabbit = {
jumps: true
__proto__ = animal;
};
// we can find both properties in rabbit now:
console.log(rabbit.eats ); // true
rabbit.walk(); // Animal walk
const obj = {
firstName: "Neeraj",
lastName: "Kumar",
getFullName: function () {
return this.firstName + " " + this.lastName;
}
};
const obj2 = {
firstName: "Er Neeraj",
__proto__: obj
};
console.log(obj2.getFullName()); //Er Neeraj Kumar
Creating own prototype
Creating Ployfill for bind method
const obj = {
firstName: "Neeraj",
lastName: "Kumar"
};
function getFullName(state) {
return this.firstName + " " + this.lastName + " " + state;
}
const fName = getFullName.bind(obj, "Yadav");
console.log(fName()); //Neeraj Kumar Yadav
Function.prototype.myBind = function (...args) {
const func = this;
const params = args.slice(1);
return function () {
return func.apply(args[0], params);
};
};
const fName2 = getFullName.myBind(obj, "Roy");
console.log(fName2()); //Neeraj Kumar Roy
Creating Ployfill for Call, Apply and Bind method
const obj = {
firstName: "Neeraj",
lastName: "Kumar"
};
function getFullName(state) {
return this.firstName + " " + this.lastName + " " + state;
}
Function.prototype.myBind = function (obj, ...args) {
obj.func = this;
return () => {
return obj.func(...args);
};
};
Function.prototype.myCall = function (obj, ...args) {
obj.func = this;
return obj.func(...args);
};
Function.prototype.myApply = function (obj, args) {
obj.func = this;
return obj.func(...args);
};
const fName2 = getFullName.myBind(obj, "Yadav");
console.log(fName2()); //Neeraj Kumar Yadav
console.log(getFullName.myCall(obj, "Roy")); //Neeraj Kumar Roy
console.log(getFullName.myApply(obj, ["Sonu"])); //Neeraj Kumar Sonu
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